Research on patient outcomes related to Ventilator-Associated Pneumonia (VAP), an infectious disease, are a focus of the Chronic Conditions and Infectious Disease Core Science area of the National Institute of Nursing Research. A less invasive and costly diagnostic marker of VAP is needed for nurses to signal prompt diagnosis and treatment of VAP to restore health and prevent pulmonary disease. Currently, the clinical diagnosis of VAP includes non-specific symptoms that limit the reliance on clinical parameters as a diagnostic tool. Suspected clinical cases of VAP are diagnosed using Broncheoalveolar lavage (BAL), an invasive and costly procedure that requires physician-directed access to the lower respiratory tract in order to retrieve a sample of the lung flora. The delay in time for accurate pathogen identification using this method contributes to unnecessary delay in appropriate treatment or prolonged treatment with unnecessary antibiotics, contributing to antimicrobial resistance. The use of BAL is limited in some settings due to the need for additional personnel, equipment, and time required by the procedure. Recent preliminary evidence suggest that soluble triggering receptor expressed on myeloid - 1 cells (sTREM-1) in exhaled breath condensate (EBC) offers promise as a noninvasive, early biomarker of VAP. Project Summary: This two year study will determine the utility of using a biomarker (sTREM-1) in the EBC and BAL fluid of patients with clinically suspected VAP in the critical care environment of a regional level-one trauma center. Previously collected and stored samples will be analyzed for the presence of sTREM-1 and compared to quantitative culture of BAL fluid (the current diagnostic gold-standard) for sensitivity, specificity, and predictive values. Purpose: This study will compare the diagnostic utility of a single measurement of sTREM-1 in exhaled breath condensate (EBC) and broncheoalveolar lavage (BAL) fluid as biomarkers of VAP in intubated and mechanically ventilated critically ill adult patients using quantitative culture of pathogenic isolates from culture of BAL fluid, CPIS, and clinical criteria as reference standards for VAP diagnosis. Aims are to: 1) describe the relationship between sTREM-1 in BAL and EBC fluids;2) compare the sensitivity, specificity, and predictive values of sTREM-1 in BAL fluid with two reference standards (clinical criteria, and pathogenic isolates cultured from BAL fluids);and 3) compare the sensitivity, specificity, and predictive values of sTREM-1 in EBC fluid with two reference standards (clinical criteria, and pathogenic isolates cultured from BAL fluid). Methods: Prospective cohort design to test for association between variables. Relevance to Public Health: Improving the early diagnosis of VAP through non-invasive methods performed at the bedside will save lives and costs and improve patient outcomes through the appropriate and early use of antimicrobials.